Frequency microcomb stabilization via dual-microwave control

Abstract Optical frequency comb technology has been the cornerstone for scientific breakthroughs in precision metrology. In particular, unique phase-coherent link between microwave and optical frequencies solves long-standing puzzle of synthesis. While current bulk mode-locked laser had great success extending frontier, its use real-world applications beyond laboratory setting remains an unsolved challenge due to relatively large size, weight power consumption. Recently microresonator-based combs have emerged as a candidate solution with chip-scale implementation scalability. The wider-system control stabilization approaches microcombs, however, requires external nonlinear processes multiple peripherals which constrain their application space. Here we demonstrate internal phase-stabilized microcomb that does not require second-third harmonic generation nor references. We can be stabilized by two internally accessible parameters: intrinsic offset ? spacing f rep . Both parameters are phase-locked references, phase noise residuals 55 20 mrad respectively, resulting comb-to-comb uncertainty is 80 mHz or less. Out-of-loop measurements confirm good coherence stability across comb, measured instability 2 × 10 ?11 at 20-second gate time. Our supported analytical theory including cavity-induced modulation instability. further describe our technique low microwaves suppression repetition rate below limit achieved.